The objective of this study was to characterize the clinical features and natural history of primary lateral sclerosis (PLS).
PLS is a motor neuron disorder defined by corticospinal and corticobulbar tract dysfunction without clinically significant lower motor neuron involvement.
We collected data from 25 patients with PLS seen in 2 academic neurology departments over a 5-year period.
The PLS population represented approximately 3% of acquired motor neuron disease cases seen during that period. Twenty-three patients (92%) presented with lower limb weakness, spasticity, or difficulty with ambulation. None presented with upper limb symptoms. Eleven patients (44%) developed bulbar symptoms. All patients had hyperreflexia and increased muscle tone. Muscle weakness was observed in 15 patients (60%) and tended to be mild and asymmetric. Needle electromyography (EMG) was normal or showed only fasciculations in 15 patients (60%); 10 patients had features of mild active denervation, consisting of fibrillation or positive sharp wave potentials, but the extent of these findings did not satisfy World Federation of Neurology electrophysiological criteria for the diagnosis of amyotrophic lateral sclerosis. Fourteen patients (52%) continued independent ambulation. Of the 10 patients with active denervation on EMG, 6 (60%) required a walker, scooter, or wheelchair at a mean follow up of 6.2 years. There were no fatalities over the 5-year period.
Our experience supports the observation that PLS progresses more slowly than other forms of acquired motor neuron disease, particularly amyotrophic lateral sclerosis. Follow-up data suggest that patients with active denervation changes develop greater disability.